Coordinates of non-animated object in frames with python [v.2.77]
Replace

bpy.context.scene.frame_current = i
bpy.context.scene.update()


with

bpy.context.scene.frame_set(i)


scene.frame_current = x might appear to work as expected in the python console, but in scripts like in you q, which demonstrates why not to use it, as its value not used in the scripts execution.